The injector is a medical instrument used commonly and in large quantities in the medical field. If the injector is used repeatedly, it is apt to lead to the spread of diseases between various patients and result in the cross contamination, which endanger the public health. Some people collect the waste single-use injectors that have already been used, and sale them in the medical market again for the illegal benefits, which bring the enormous hidden dangers of propagation and spread of various diseases. Moreover, when the medical personnel injects, the exposed needle may stab the medical personnel or the collector of castoff thereby causing the infection and propagation of diseases. In order to prevent the injector from being reused and achieve the object of single use by destructing the injector automatically after being used once, and in order to prevent the occurrence of accidental stabbing by the used injector, the technical schemes of the single-use injector with retractable syringe needle are proposed, such as the Chinese utility model patent No. ZL01221139.7, which disclosed a safety self-destructing single-use injector with the needle retracting into the inside of the injector after injecting. This technical schemes includes fixing the needle in the needle stand with a casing spring, the needle stand then being fixed in the head portion of the injector with the needle gasket, and at the end of injection, the pushrod's bottom plug fixed on the head of pushrod releasing the fit between the needle stand and the gasket through pushing and pressing, while the pushrod's bottom plug being pressed into the inside of hollow pushrod, and the whole needle together with the needle stand being retracted backward to the inside of the pushrod under the action of the spring, thereby achieving the self-destruction of injector so as to its reuse is avoided and the occurrence of stabbing accident due to the exposure of the needle after injection is excluded.
Though this technical scheme can carry out the retraction of the injector's needle after injection, the retraction process is performed automatically and is uncontrollable. Therefore, the technical solution exists the disadvantages as follows: first, the retraction is performed when the needle still stays in the patient's body while the injection is finished, which may cause the needle to push forward or sway when releasing the fixed structure of needle stand, thereby paining the patients or even hurt them; second, according to the operation criterion, the medical personnel should press the injection location with the sterilized cotton ball at the end of injection and then draw out the needle. However, the retraction of needle is automatic in this technical scheme and can not be controlled by the medical personnel, so the medical personnel must press the injection location with the sterilized cotton ball before the end of injection, which brings the operational inconvenience for the medical personnel because they must change their customary injection practice.
And in the technical scheme, the fixed structure of needle stand also exists defects that it can not obtain the fixed effect of being firm as well as releasable. Furthermore, the technical scheme also exists the defects that the needle stand is pushed forward to further penetrate into the patient's body when the bottom plug of the pushrod pushes and presses the fixed structure of needle stand and that the residual liquor is too much.